Method and apparatus for manufacturing trace performing parts with aspherical surfaces

ABSTRACT

A method and apparatus for aspherical manufacturing are disclosed using trace performing. On a cone, a section whose trace corresponds to that of a required curve is defined by mathematical calculation, i.e. the parameters of the section is defined. The cone is installed to a position that provides with a trace intersection, the trace intersection couples with a grinding wheel, the cone links with the part, the part is rotated and swung about a swing axis with the cone, the trace intersection fixedly connects to the grinding wheel. Whereby the curve trace intersected on the cone is accurately transferred to the part during the performing. The present invention can be used in performing parts with convex/concave conic and high-order aspherical surfaces and has advantage in general utility, precision, efficiency and costs.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for themachining of aspherical optical parts.

2. Description of the Related Art

The aspherical parts in optical systems have not been widely usedbecause of the difficulty of machining and inspecting such parts,although the advantages of using them, rather than spherical parts, areconsiderable. And these advantages have led to extensive research ondiscovering a machining and inspection process, to speed up thedevelopment and application of aspherical surface technology.

The methods that have been excogitated out to machine aspherical partsso far are more than twenty kinds, which can be classified into fourgroups: according to the machining principle they employed, excisionmachining, appending machining, transmogrification machining andmetamorphosing machining. Although there are so many different machiningmethods, except the conventional manual machining, or numerical controlmachining, most of them are aiming at an aspherical surface with aparticular shape and dimension. None of these methods can achieve a highefficiency, machining precision and universality within the sameprocess.

At present, excision machining is the method most commonly used tomachine small-batch aspherical optics parts both in home and abroad. Theprocess includes conventional manual milling and polishing or numericalcontrol turning, or numerical control milling and polishing, ornumerical control grinding. Although the conventional manual milling andpolishing method can attain a high precision aspherical part, theoperator must be rich experienced and highly skilled, in addition topoor quality in its repeat performance, long machining period, and itshigh cost, this method cannot meet the requirements of batch production.For a long time, in order to solve the problems of long productionperiod and high cost, people have been exploring in field of locusshaping by mechanism or mould copying. Although such a machining methodwould be efficient and ensure attainment of a good surface quality, itis still difficult to obtained high precision aspherical parts becausethe figure shaped by the locus shaping method has a significant profileerror. Furthermore, it cannot meet the need for the varying shapes anddimensions of aspherical optics parts machined because of the immobilityof the locus shaped by mechanism or mould copying. Therefore, it canonly be used in batch production of a certain fixed shape and dimensionof aspherical optics part requiring low or medium-range precision.

With the development of numerical control technology, people abandon themethod of locus shaping by mechanism or mold copying, and turn to methodof numerical control technology to solve the problems in machining ofaspherical parts. The essence of method of numerical control technologyis to gradually approach the surface or figure of design by usingnumerical control milling and polishing method. Alternatively, theaspherical surface can be attained by numerical control turning orgrinding to move the lathe tool or grinding-wheel according to the trackorders programmed. Numerical control machining is a kind of flexiblemachining technique, so it can meet the needs of varying shapes anddimensions of aspherical optical parts machining. But high precisionaspherical surfaces can be attained only after inspection andmeasurement has been completed and finishing and milling have beenfrequently repeated. Furthermore, the machining equipment is expensive,and because it belongs to an area of expert operational technology, theoperational techniques are complicated. And even though it can be usedto machine high precision aspherical surfaces, it cannot meet the needof batch production because of the long machine period and its highcost. At present, there is no a single type of high efficient machiningtechnology that can be used in both machining individual asphericaloptics parts and batch production of aspherical optics parts.

The history of methods of machining aspherical optics parts has been thedevelopment from conventional manual machining to locus shaping bymechanism or mould and die copying, then to numerical control machining.From this development renovation, we can see that the key question ishow to get a method of obtaining an accurate locus of aspherical surfaceshaping and machining high precision aspherical parts accurately andefficiently.

There are many types of aspherical surfaces which can be used in aoptical system. Most of them are axis symmetrical aspherical surfacesand their machining is very difficult. Most of the axis symmetricalaspherical surfaces are composed of curves such as ellipses, parabolasand hyperbolas, in addition, there are also some high order asphericalsurfaces.

SUMMARY OF THE INVENTION

The present invention is directed to a method and apparatus for themachining of aspherical optics parts with locus shaping, to resolve theproblems identified above, of meeting the need of varying shape anddimension aspherical optics parts production both individually and bybatch production, in a high efficient and low cost way.

The invented method of machining includes a process of coarse grinding,finishing grinding and super-finishing grinding (or polishing) of convexor concave surfaces of conic and high-order aspherical type.Characterized in that, the specific steps for machining conicalaspherical optics parts comprising:

In a first step, according to the conic equation given by the designer,the section parameters of α, φ and L on a cone that decide the accuratelocus needed are deduced by mathematical calculation, Or the appropriatecurve locus is decided by trial-machining;

In a second step, the locus is intercepted on a cone by a transversalintercept object, and the cone is fixed on apparatus for machiningaspherical optics parts with locus shaping, so that the transversalintercept object is mounted, then the relative position between them isestablished in terms of the parameters deduced above;

In a third step, the part is swinging around a swing-axle with the conewhile it is rotating, then the accurate locus curve intercepted on thecone is accurately transferred to the part during the machining and anaspherical surface is shaped, that is, the locus intercepted can betransferred accurately to the part during machining and conicalaspherical optics parts are obtained; and convex or concave high-orderaspherical optics part can be obtained as follows: an accurate planeoutline template, with a high-order curve profile made by other methods,is used to replace the cone fixed on the apparatus, and that is, thehigh-order curve profile on the plane outline template can betransferred accurately to the part during machining, and high-orderaspherical optics part will be obtained.

This invention, additionally, specifies the apparatus to be used for themachining method outlined above. The apparatus comprising: swing-table,thrust-block, thrust-parts, part-axis-drive-electromotor,cone-move-screw, guidance-seating, part-fixing-shaft, backstop-seating,grinding-wheel, buttress-rack, locus-intercept-object, cone, lathe-bed,swing-axle, swing-axle-electromotor and part-axle-box,

-   the grinding-wheel sits on the buttress-rack;-   the forward-and-backward and up-and-down mobile    locus-intercept-object is fixed on the buttress-rack;-   the buttress-rack is fixed on the lathe-bed;-   the cone, whose angle can be adjusted, sits on the backstop-seating;-   the backstop-seating is fixed on the guidance-seating;-   the guidance-seating can be slid along the guidance-orbit located in    the bottom of the part-axle-box;-   the swing-axle-electromotor drives the swing-table to swing around    the swing-axle, the part is clamped on the forepart of the    part-fixing-shaft, it swings around the swing-axle with half    stretched angle of the part while it is rotating,-   the thrust-block is fixed on the swing-table;-   the thrust-parts are fixed between the thrust-block and the    part-axle-box, so as to keep the cone in constant contact with the    locus-intercept-object,    The axes of the part-fixing-shaft, cone, and swing-axle are required    to be co-planar in the vertical plane. The axes of the    part-fixing-shaft and grinding-wheel are required to be co-planar in    horizontal plane.

This process can be used to machine aspherical optics parts ormechanical parts of glass, porcelain, crystal or metal.

This invention is the apparatus and method for machining asphericaloptics parts, wherein using innovative principle of interceptingaccurate locus defined by the designer's conic equation and innovativetechnology of accurately transferring the locus intercepted to the partduring the machining and thus obtaining the aspherical optics part.

The benefits of this invention are as follows:

1. Universality: all the conic curves of different parameters we needed,such as circle, ellipse, parabola or hyperbola can be intercepted fromthe cone 13 and the intercepted curves are proper.

2. High precision: the accurate values of section parameters α, φ and Lcan be calculated by formula deduced according to the conic equationy²−ƒ(x) given by the designer. Thus, an accurate locus of the conicequation as given can be ascertained easily and precisely.

3. Simplicity and reliability of the locus transfer mechanism: Byfine-tuning to adjust the value of φ and L, the surface profile errorcan be eliminated. As a result, the locus of the curve intercepted canbe accurately transferred to part 9 and a high precision asphericalsurface can be obtained.

4. High efficiency and low cost: Because the locus can be easily andaccurately intercepted and it can be transferred accurately at the sametime. Furthermore, the working procedures of coarse grind, finishinggrind and super-finishing grind (or polishing) can be carried out withinone load and clip.

5. Simple operation: It is not necessary to employ an expert to operatethe apparatus, and there are few technical requirements for an operator,so it is easy to spread widely.

In conclusion, applying the technology of this invention to themachining of aspherical optics parts can resolve the difficult problemsof machining mentioned hitherto. Its efficiency and costs will be closeto that of current methods of machining spherical optics parts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the intercept locus on a cone.

FIG. 2 illustrates the apparatus to machine a convex aspherical opticspart.

FIG. 3 illustrates the apparatus to machine a concave aspherical opticspart.

FIG. 4 illustrates the apparatus to machine a concave aspherical opticspart using a cylindrical grinding-wheel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is illustration of intercepting locus on a cone, where thehalf-apex-angle of the cone is α, point A is the vertex of the cone,point D lies on a generatrix of the cone, while the distance betweenpoint A and point D is L. If the cone is intercepted by a plane denotedas a-a, and the angle between the plane and the axes of the cone is φ1=90, a locus defined by circularity curve equation is obtained as aresult. If intercepted by a plane denoted as b-b, and the angle is90>φ2>α, a locus defined by elliptical curve equation is obtained as aresult. If intercepted by a plane denoted as c-c, and the angle is φ3=α,a locus defined by parabola curve equation is obtained as a result. Ifintercepted by a plane denoted as d-d, and the angle is α>φ3>−α, a locusdefined by elliptical curve equation is obtained as a result. In anycase, as long as the relative section parameters of α, φ and L on a coneare deduced according to any locus defined by the designer's conicequation, the locus can be intercepted from the cone. By mathematicalcalculation, the values of α, φ and L can be fixed accurately, or theappropriate curve locus is decided by the method of trial-machining. Infact, the half-apex-angle of the cone α is invariant and decided when itis machined. So that, only φ and L are needed to calculated in order tointercepting a designed curve.

The detailed method and technology for intercepting accurate locus andaccurately transferring locus to the part have been shown in FIGS. 2, 3and 4. The position of cone 13 and locus-intercept-object 12 areaccurately decided by the accurate values of α, φ and L deduced. Andmaking the distance between the aspherical part 9 and the center of acircle minimum, and it is aligned with the axis of swing-axle 15, andthe contact point D of locus-intercept-object 12 and cone 13 is alignedwith the grinding face of the grinding-wheel to the same vertical line.And under a little thrust force, the cone 13 and locus-intercept-object12 are contacting all the time. And then, swing-axle-electromotor 16 isstarted to drive the swing-table 1 to swing, in this way, the accuratelocus can be lined out on the cone which is given by the designer'sconic equation. On this base, starting the grinding-wheel 10 and part 9turning, and let the part move a little to the grinding-wheelsimultaneously. Then, the grinding-wheel grinds out the allowance of thepart accurately according to the intercepted locus, after grinding manytimes, all allowance are grinded out, and then the intercepted locuswill be accurately transferred to part 9. The high precision conicaspherical surface is obtained, which is identical with the locus givenby the designer's conic equation.

FIG. 2 illustrates an apparatus to machine a convex aspherical opticalpart. It is made up of swing-table (1), thrust-block (2), thrust-parts(3), part-axis-drive-electromotor (4), cone-move-screw (5),guidance-seating (6), part-fixing-shaft (7), backstop-seating (8),grinding-wheel (10), buttress-rack (11), locus-intercept-object (12),cone (13), lathe-bed (14), swing-axle (15), swing-axle-electromotor (16)and part-axle-box (17). Part 9 is rotating around the part-fixing-shaft(7). While together with the cone (13), it swings around swing-axle (15)along with the swing-table (1) in the range of the half-vertex-angle ofthe part. Cone (13) is in tight contact with locus-intercept-object (12)under the action of spring thrust-parts (3), a part-axle-box (17) is seton this apparatus, it can slide lengthways along the swing-table (1).Between the thrust-block (2) fixed on swing-table (1), and part-axle-box(17), thrust-parts (3) is set. The thrust-parts (3) shown in FIG. 2 is aspring, which can be replaced by a heavy hammer. Locus-intercept-object(12) can be set on buttress-rack (11) or lathe-bed (14), which can bemoved forward and backward, up and down. The end oflocus-intercept-object (12) is aligned with the outer circle grindingface of grinding-wheel (10) in the vertical plane, to ensure that thelocus will be intercepted and transferred to part (9) accurately. Thegrinding-wheel (10) is also set on buttress-rack 11, it is fixed withlocus-intercept-object 12 as a whole, cone (13) is set onbackstop-seating (8), the angle φ between axes of cone (13) andswing-axle (15) can be adjusted to attain a calculated one.Backstop-seating (8) is fixed on guidance-seating (6) which is fixed onthe guidance in the bottom of part-axle-box (17). By means of rotatingcone-move-screw (5), guidance-seating (6) can slide along the guidepulley, which moves cone (13) to and fro. When cone (13) moves backward,part-axle-box (17) moves forward. Then part (9) comes into contact withgrinding-wheel (10), consequently the allowances of the part is removed,simultaneously the curve locus is transferred accurately to part (9) anda convex aspherical surface comes into being, which is intercepted fromcone (13) with locus-intercept-object (12).

FIG. 3 and FIG. 4 illustrate the machining of a concave asphericalsurface. The radius of grinding-wheel (10) is less than the radius ofpart (9). For a concave aspherical surface with a large radiuscurvature, a grinding-wheel with disc shape must be used as shown inFIG. 3. For a concave aspherical surface with a small radius curvature,a grinding-wheel with cylindrical shape must be used as shown in FIG. 4.

If a high order aspherical optics part is to be machined, the coneshould be replaced by a concave or convex high order aspherical planetemplate.

FIG. 2 illustrates the machining of a convex aspheric surface, whereinthe contact point D of cone (13) and locus-intercept-object (12) are onthe right of the axes of swing-axle (15). FIG. 3 and FIG. 4 illustratethe machining of a concave aspherical surface, wherein the point D is onthe left of axis of swing-axle (15), and it is possible to work onlywhen the radius of grinding-wheel is less than the curvature radius ofthe part.

In this invention, the purpose can also be achieved if some changes aremade in the apparatus as follows: grinding-wheel, set on swing-table 1,is swinging while it is rotating, part (9) is only rotating which is seton buttress-rack (11), the position of cone (13) andlocus-intercept-object (12) are exchanged with each other.

The above preferred embodiment is merely exemplary and is not to beconstrued as limiting the present invention. The equivalentmodifications or decorations of this invention in the scope of theclaims are all protected.

1. A method for machining aspheric with locus shaping, comprising themachining of coarse grind, fine grind, and super-finishing grind (orpolishing) to a convex or concave surfaces of quadratic and high-orderaspheric; and characterized in that, the specific steps for machiningconical aspherical optics parts comprising: in a first step, accordingto the conic equation given by the design, deduce the section parametersof α, φ and L (see FIG. 1) on a cone to decide the accurate locus, orthe appropriate curve locus is decided by trial-machining; in a secondstep, the locus is intercepted on a cone by a transversal interceptobject, and the cone is fixed on apparatus for machining asphericaloptics parts with locus shaping, so that the transversal interceptobject is mounted, then the relative position between them isestablished in terms of the parameters deduced above; in a third step,the part is swinging around a swing-axle with the cone while it isrotating, then the accurate locus curve intercepted on the cone isaccurately transferred to the part during the machining and anaspherical surface is shaped, that is, the locus intercepted can betransferred accurately to the part during machining and conicalaspherical optics parts are obtained; and convex or concave high-orderaspherical optics part can be obtained as follows: an accurate planeoutline template, with a high-order curve profile made by other methods,is used to replace the cone fixed on the apparatus, and that is, thehigh-order curve profile on the plane outline template can betransferred accurately to the part during machining, and high-orderaspherical optics part will be obtained.
 2. The method of claim 1,characterized in that, a convex aspherical optics part is obtained whenthe contact points of the cone and locus-intercept-object axes are onthe right of the swing-axle.
 3. The method of claim 1, characterized inthat, a concave aspherical optics part is obtained when the contactpoints of the cone and locus-intercept-object axes are all on the leftof the swing-axle, and the radius of the grinding-wheel must be lessthan the curvature radius of the part.
 4. The method of claim 1,characterized in that, when the position of the cone and thelocus-intercept-object is decided, in order to remove the redundantarea, the part is allowed to move towards the grinding-wheel. Thecontact point of the locus-intercept-object and cone mentioned here isaligned with the working face of the grinding-wheel to the same verticalline. The method of claim 1, characterized in that, it can machineaspherical optics parts or mechanical parts of glass, porcelain, crystalor metal materials.
 6. The apparatus of claim 1, characterized in that,comprising (see FIG. 2): a swing-table (1), thrust-block (2),thrust-parts (3), guidance-seating (6), part-fixing-shaft (7),backstop-seating (8), grinding-wheel (10), buttress-rack (11),locus-intercept-object (12), cone (13), lathe-bed (14), swing-axle (15),swing-axle-electromotor (16) and part-axle-box (17), and Thegrinding-wheel (10) sits on the buttress-rack (11), thelocus-intercept-object (12), which can be moved forward and backward, upand down, sits on the buttress-rack (11), The cone (13), the angle ofwhich can be adjusted, sits on the backstop-seating (8), Thebackstop-seating (8) sits on the guidance-seating (6), which can be slidalong the guidance lay in the bottom of the part-axle-box (17), thepart-axle-box (17) can be slid lengthways on the swing-table (1), theswing-axle-electromotor (16) drives the swing-table (1) to swing aroundthe swing-axle (15), part (9) sits on the front part of thepart-fixing-shaft (7), together with the cone (13), it swings around theswing-axle (15) along with the swing-table (1) in the range protractedby the half-apex-angle of the part, the thrust-block (2) is fixed ontothe swing-table (1), the thrust-parts (3) are set between thethrust-block (2) and the part-axle-box (17) to keep the cone (13) andthe locus-intercept-object (12) in constant contact.
 7. The apparatus ofclaim 6, characterized in that, the grinding-wheel (10) can be a diskshape one or a cylinder shape one, and when convex aspherical parts aremachined, the disk grinding-wheel can be made up of one, two or threedisks.
 8. The apparatus of claim 6, characterized in that, the axes ofthe part-fixing-shaft (7), the cone (13), and the swing-axle (15) arerequired to be co-planar in the vertical plane. The axes of thepart-fixing-shaft (7) and the grinding-wheel (10) are required to beco-planar in horizontal plane.
 9. The apparatus in claim 6,characterized in that, if the grinding-wheel (10), on the swing-table(1), swings while it is rotating, And part (9) only rotates when it isset on the buttress-rack (11), and the positions of the cone (13) andthe locus-intercept-object (12) are exchanged, then the machiningpurpose of this invention can also be achieved.
 10. The apparatus inclaim 6, characterized in that, if a convex or concave plane outlinetemplate with high-order curve profile is substituted for the cone (13),then a convex or concave high-order aspherical part can be machined.